An oral preparation may impart a displeasing feel (e.g., bitterness or astringency) due to the medicine or may cause nausea or medication refusal so that medication compliance may deteriorate. For example, a solid preparation (e.g., powder or tablet) which is a general form of an oral preparation can be swallowed only with difficulty if administered as is. Therefore, a solid preparation is usually administered together with a large amount of water, resulting in a decrease in medication compliance. In particular, elderly persons and children have difficulty in swallowing a solid preparation in many cases. In addition, the preparation may accidentally block the throat or become attached to the esophagus, which may cause an esophageal tumor.
In order to increase ease and safety of administration, an oral preparation a having water-swellable gel-forming layers 12 and 12′ laminated on either side of a medicine 13 as shown in FIG. 10(a) has been proposed (Patent Documents 1 and 2).
When the oral preparation a is put into the patient's mouth, the water-swellable gel-forming layers are swollen and gelled by moisture such as saliva, whereby the preparation a changes into a form having a more easily administered size, shape, elasticity, viscosity, and the like and can be safely provided to elderly persons and infants without a danger of blocking the throat. In the case of a patient who can discharge only an insufficient amount of saliva to cause the water-swellable gel-forming layers to be sufficiently swollen and gelled, the preparation a can exhibit the same effect if administered together with a small amount of water or after being immersed in water. The amount of water used in such a case is very small as compared with the amount of water necessary for other solid preparations such as tablets and capsules.
When the oral preparation a is put into the patient's mouth, the water-swellable gel-forming layers are swollen and gelled by moisture such as saliva, causing the medicine-containing layer to be covered with the gel. The gel has an effect of masking the taste (bitterness, astringency, etc.) and odor of the medicine contained in the medicine-containing layer, whereby a decrease of medication compliance can be prevented.
However, the medicine 13 is exposed on the ends of the oral preparation a shown in FIG. 10(a). The medicine 13 in these areas cannot be completely covered with a gel and some portion is left exposed even if the water-swellable gel-forming layers 12 and 12′ are swollen and gelled by moisture such as saliva. For this reason, it has been difficult to completely mask the taste and odor of the medicine 13 of the oral preparation a.
Therefore, another oral preparation which can completely mask the taste and odor of the medicine contained in the medicine-containing layer as shown in b of FIG. 10(b) has been proposed in Patent Document 3.
The oral preparation b described in Patent Document 3 is prepared as follows.
A suspension containing a water-swellable gel-forming agent and the like is applied to the surface of a first support such as a plastic film, and dried to form a water-swellable gel-forming layer 14′. A suspension containing an adhesive is applied to the surface of the water-swellable gel-forming layer 14′, and dried to form an adhesive layer 15′. A first laminate in which the water-swellable gel-forming layer 14′ and the adhesive layer 15′ are sequentially laminated on the support can be obtained in this manner.
A second support is provided, and a water-swellable gel-forming layer 14 and an adhesive layer 15 are sequentially laminated on the surface of the second support. Next, a suspension containing a medicine and the like is applied to the surface of the adhesive layer 15, and dried to form a medicine 13. In this instance, the lower side of the medicine 13 is made smaller than the upper side of the adhesive layer 15. That is to say, the medicine 13 is formed at the center of the upper side of the adhesive layer 15 so that the periphery of the upper side of the adhesive layer 15 is left exposed. In this manner, a second laminate in which the water-swellable gel-forming layer 14, the adhesive layer 15, and the medicine 13 are sequentially laminated on the second support can be obtained.
Next, the periphery of the water-swellable gel-forming layer 14′ of the first laminate is bonded to the periphery of the water-swellable gel-forming layer 14 via the adhesive layers 15 and 15′ to obtain an oral preparation b having the medicine 13 sealed therein.
However, the above method of producing the oral preparation b allows only a limited amount of medicine to be included therein, and subjects the medicine to significant heat history by which the medicine may be denatured. In addition, the method of producing the oral preparation b has a problem of poor industrial productivity due to the requirement of making the lower side of the medicine 13 smaller than the upper side of the adhesive layer 15.    Patent Document 1: WO 02/087622    Patent Document 2: JP-A-2005-298471    Patent Document 3: JP-A-2005-289868